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ABSTRACT:The effects of different color pigments on the durability of wood-flour/high-density polyethylene composites (WF/HDPE) were evaluated by UV-accelerated weathering tests. WF/HDPE composites were dyed using three different color inorganic pigments, which were added at 2% based on the weight of the composite. Samples were weathered in Q-panel UV aging equipment for 1500 h. All samples showed significant fading and color changes in exposed areas. Changes in surface chemistry were studied using spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) was used to verify the occurrence of surface oxidation. Changes in carbonyl groups (C¼ ¼O), PE crystallinity, cellulose CAO, and lignin aromatic C¼ ¼C were detected by Fourier transform infrared (FTIR) spectroscopy. The results indicate that surface oxidation occurred immediately within exposure 250 h for all samples; the surface of the control WF/HDPE composites was oxidized to a greater extent than that of the dyed WF/HDPE. This suggests that the addition of pigments to the WF/HDPE composites results in less weather-related damage. The surface configuration observed by scanning electron microscopy revealed that WF/HDPE composites degraded significantly on accelerated UV aging, with dense cracking apparent on the exposed surface. Carbon black had a more positive effect on color stability than the other pigments.

The influence of plant-based (gum arabic and quillaja saponin) and animal-based (whey protein isolate, WPI) emulsifiers on the production and stability of vitamin E-fortified emulsions was investigated. Their impact on lipid digestibility and vitamin bioaccessibility was also studied utilizing an in vitro gastrointestinal tract. WPI and saponin produced smaller emulsions than gum arabic. All emulsions had good storage stability at room temperature (4 weeks, pH 7). Saponin-and gum arabic-emulsions were resistant to droplet aggregation from pH 2 to 8 because these emulsifiers generated strong electrosteric repulsion. WPI-coated droplets flocculated around pH 5 due to a reduction in charge near their isoelectric point. Lipid digestion was slower in saponin-emulsions, presumably because the high surface activity of saponins inhibited their removal by bile acids and lipase. Vitamin bioaccessibility was higher in WPI-than in saponin-or gum arabic-emulsions. This information may facilitate the design of more efficacious vitamin-fortified delivery systems.

MA modified wood flour/PLA composites were prepared by one-step reactive extrusion, in which wood flour and poly(lactic acid) (PLA) were used as raw material, maleic anhydride (MA) was used as modifier, and dicumyl peroxide (DCP) was used as initiator. The influences of MA concentration on the morphology, thermal stability, rheological, and mechanical properties of the composites were studied. The addition of MA improved the compatibility of the composites significantly. The thermal and rheological results showed that with the increase of the concentration of MA, the thermal stability of the composites decreased, the storage modulus and complex viscosity of the composites also decreased. The MA modified composites had an enhanced mechanical strength compared to the unmodified one. As the concentration of the MA increased, the tensile and flexural strength of the composites first increased and then decreased, and reached a maximum when the concentration of MA was 1 wt %. The MA modified composites showed a better water resistance than the unmodified ones.

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